Semirigid foldable boat

ABSTRACT

A lightweight foldable boat comprised of substantially flat elongated flexible elements positioned so as to form side and bottom panels, said panels being spatially secured to each other at their extremities and adjacent edges by a foldable material impervious to liquids and the like thereby defining an elongated open faced vessel. A removable expansion member, which is slightly larger in width and depth then the width and depth of the formed vessel prior to the expansion of the latter, is positioned in the midsection of the vessel in tensional engagement with the side and bottom panels thereof, thereby outwardly bowing the same. A removable locking member is inserted to engage the expansion member so as to maintain the latter in tensional engagement with the side and bottom panels, said locking member being engaged with the side panels to prohibit movement of the locking member in a plane normal to said locking member, accordingly preventing subsequent displacement of the expansion member thereby maintaining the side and bottom panels in a substantially rigid outwardly bowed position.

United States Patent N ovakovich [45] Mar. M, W72

[54] SEMIRIGID FOLDABLE BOAT [57] ABSTRACT [72] Inventor: Milan Novakovich, 2l5 Apolena Avenue, A lightweight foldable boat comprised of substantially flat Balboa island, Calif. 92662 elongated flexible elements positioned so as to form side and bottom panels, said panels being spatially secured to each [22] Wed: Sept 1970 other at their extremities and adjacent edges by a foldable [21] APPL 73,722 material impervious to liquids and the like thereby defining an elongated open faced vessel. A removable expansion member, which isslightly larger in width and depth then the width and [52] US. Cl ..9/2 F depth of the formed vessel prior to the expansion 0f the latter, [5]] Int. Cl "8631) 7/06 is positioned in the midgection of the vessel in tensional en- [58] Field of Search ..9/2 F, 2 C, 2 R, 6 gagement with the side and bottom panels thereof. thereby outwardly bowing the same. A removable locking member is 56] References Cited inserted to engage the expansion member so as to maintain the latter in tensional engagement with the side and bottom UNITED STATES PATENTS panels, said locking member being engaged with the side 1 895 380 1/1933 panels to prohibit movement of the locking member in a plane 2830308 4/1958 normal to said locking member, accordingly preventing sub- 16496 1/1964 sequent displacement of the expansion member thereby maintaining the side and bottom panels in a substantially rigid out- 3l39634 7/1964 wardly bowed position 3,529,312 9/1970 Primary Examiner-Milton Buchler Assistant ExaminerCarl A. Rutledge Attorney-Roman A. Di Meo IIMM ,BAELBOS FATENTEUMAR 1 & m2

SHEET 1 BF 3 INVENTOR M/LAA/ NOV/4 owa/ PATENTEHMAR m We $6M 309 sum 3 [1F 3 PMENTEBMAR 14 I972 3 6A8 309 SHEET 3 [IF 3 INVENTOR M/A/V NOVAKOV/CH SEMIRIGID FOLDABLE BOAT This invention relates to foldable boats, and more particularly to boats which can be easily folded to conserve storage space and facilitate the portability thereof.

With the advent of increased leisure time of individuals and the concomitant increased demand for recreationally oriented activities, particularly pleasure boating, camping, fishing and the like, a large demand has developed for relatively small boats which are of light weight and are compact or reducible to smaller sizes so that when not in use little storage or carrying space is required.

Heretofore small boats such as sabots, dinghies or kayaks were of a fixed rigid dimension and relatively heavy, thereby requiring an excessive amount of storage or carrying space. Where the amount of available space is limited, such as on a pleasure boat or camper trailer, the weight and fixed size of present dinghies and the like make the latter cumbersome and undesirable to transport or store when not in use.

The present invention has overcome these disadvantages by providing a simple lightweight boat capable of being folded to a narrow thickness so as to facilitate storage and transportation thereof and which is capable of being assembled and expanded to its normal dimensions in a short period of time.

The invention is comprised of threesubstantially flat elongated flexible panels such as marine plywood or the like which are shaped to define the sides and bottom of a dinghy or a sabot. The side and bottom panels are in spatial relationship and permanently interconnected at their respective edges by a liquid-impervious foldable material such as vinyl or the like. The same liquid-impervious foldable material also connects the ends of the side and bottom panels at each extremity thereof so as to form a flat end normal to the longitudinal axis of the panels when said panels are fully expanded. It is obvious from the foregoing, that at this point an open vessel is defined lacking only struts or other means to provide a vessel with rigidity.

On the inner side of each side panel and opposite one another are channel or groove means extending normal to the major axis of the panels, and second channel or groove means extending coextensively with the major axis of the side panels, said second channel means being positioned adjacent the upper end of the first mentioned channel means. Accommodated within said first mentioned channel means normal to the longitudinal axis of the side and bottom panels, and concomitantly of the vessel, is an expansion member which has a slightly wider dimension than the maximum distance between the side panels prior to their outward expansion. Upon the insertion of the expansion member within the aforesaid first channel means, the side panels are caused to outwardly expand laterally to the axis of the vessel. Since the ends of the side panels are connected by the impervious foldable material and said ends are therefore relatively nonexpandable, the side panels will outwardly bow due to the engagement therewith by the expansion member.

The expansion member is inserted into the first mentioned channel means until it clears the channels coextending with the vessel axis. The expansion member, having a slightly greater depth dimension than the distance from said second channel means to the bottom panel prior to the expansion of the latter, will cause the said bottom panel to outwardly expand. As was the case with the side panels, the bottom panel is outwardly bowed due to the engagement therewith by the expansion member and to the restriction of the extremities thereof by virtue of the impervious foldable material interconnecting the ends of the panels. It should be noted that the apex of the bow in the side and bottom panels occurs in the area thereof contacted by the expansion member. It should be further noted that although a solid panel is illustrated to describe the expansion member, other forms such as continuous or partial frames may be used without deviating from the scope of the invention herein.

A locking member is positioned in the axially coextending channels or grooves carried on the inner side of the side panels so as to abut against the upward edge of the expansion member. Due to its accommodation within the axially coextending channels, the locking member is prevented from movement normal to the axis of the vessel and concomitantly prohibits normal displacement of the expansion member, thereby maintaining the latter in constant tensional relationship with the side and bottom panels so as to maintain the same in their outwardly bowed position. It should be noted that without deviating from the scope of the invention herein, a number of means may be used to lock the expansion member into position such as a rod or rods inserted in the axially coextending channels so as to engage the edges of the ex pansion member, or a laterally extending rod positioned along the upward edge of the expansion member, a member extending coextensively with the upward edge of the expansion member and having a width greater than said edge is preferred since said locking member can perform the additional function of providing a seat for the occupant of the boat.

The locking member, which is prevented from displacement normal to the vessel axis by its accommodation in the axially coextending channels, may, if desired, be prevented from longitudinal displacement from said channels by a pin passing through the channel and the locking member (as shown herein) or some other suitable means.

Normally extending channels or grooves may be provided at the extremities of the inner sides of the side panels at both ends of the boat into which cooperating rigid panels may be inserted thereby not only increasing the rigidity of the boat, but providing also a means for mounting a rudder or a marine outboard motor or the like at the rear end thereof.

If additional seating or rigidity is desired, axially extending channels or grooves may be positioned on the inner sides of the side panels at either or both ends of the boat adjacent the extremities of side panels and end panels so as to accommodate rigid seat panels or members. Further, the seat panel at the forward end of the boat may contain a hole or bore extending therethrough into which a mast having a sail may be inserted to provide a sailing sabot.

The boat is quickly assembled by unfolding the side panels away from the bottom panel, inserting the end panels, if any, into the normally extending channels or grooves at the ends of the side panels, inserting the expansion member into the normally extending channels or grooves in the midsection of the boat until the upper edge of the expansion member clears the axially coextending channels or grooves adjacent thereto, inserting the locking member into the axially coextending channels or grooves adjacent the normally extending grooves accommodating the expansion member, and inserting the other seat panels, if any, into the axially extending channels or grooves adjacent the ends of the side panels.

Conversely, the boat is quickly disassembled by merely removing the locking member and other seat panels, if any, from the axially coextending channels or grooves, removing the end panels, if any, and the expansion member from the normally extending channels or grooves, folding one side panel over the bottom panel and then. folding the other side panel over the previously folded side panel.

It should be noted that although the expansion and locking members and other panels herein referred to may be inserted and removed from the channels or grooves in a number of ways, it has been found that the simplest and most efficient means is to have the channels or grooves open at least at one end so that the members and panels are merely inserted in the open end of the channels or grooves and slid therein.

Accordingly, it is the primary object of this invention to provide a lightweight foldable boat which can be easily assembled and disassembled.

Another object is to provide a lightweight boat which can be easily folded into a lesser size.

Still another object is to provide a lightweight foldable boat which can be easily assembled and disassembled without the use of tools.

Yet another object of the present invention is to provide a lightweight foldable boat which can be easily converted into a sail boat or motor driven boat.

Other objects and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a side elevational view, partly sectioned, of the expanded boat ready for use;

FIG. 2 is a top plan view of the boat illustrated in FIG. 1;

FIG. 3 is a sectional view of the boat taken on the line 33 of FIG. 1;

FIG. 4 is a perspective view of the normally and axially extending channels illustrating the interrelationship thereof and the expansion and locking members;

FIG. 5 is an elevational view of the expansion member;

FIG. 6 is a side elevational view of the expansion member of FIG. 5;

FIG. 7 is a top plan view of the locking member;

FIG. 8 is a side elevational view of the locking member of FIG. 7;

FIG. 9 is a perspective view of the boat prior to the insertion of expansion, locking or other members;

FIG. 10 is a top plan view of the boat in its folded position;

FIG. 11 is a sectioned view of the folded boat taken on the line 11-11 in FIG. 10;

FIG. 12 is a fragmented, partly sectioned view of the forward end of theboat shown in FIG. 1, illustrating a sail mast passing through the forward seat thereof;

FIG. 13 is a fragmented, partly sectioned view of the rearward end of the boat shown in FIG. 1, illustrating a rudder secured thereto;

FIG. 14 is a fragmented, partly sectioned view of the midsection of the boat shown in FIG. 1, illustrating a center board well and center board passing therethrough, said center board well being secured in part by the seat locking member;

FIG. 15 is a fragmented, top plan view of the midsection of the boat shown in FIG. 14;

FIG. 16 is a perspective view of the center board well shown in FIGS. 14 and 15; and

FIG. 17 is a perspective view of the center board shown in FIGS. 14 and 15.

Referring more particularly to FIGS. 1, 2 and 3, reference numeral 15 designates generally the lightweight foldable boat of the invention herein having elongated flexible side panels 16 and bottom panel 17. It should be noted that edges 16a of side panels 16 and edges 17a of bottom panel 17 are not parallel to their respective opposite edges, thereby forming trapezoidal panels generally defining the contours of a dinghy or a sabot. It should be further noted that bottom panel 17 tapers uniformly at both edges so that the forward end is narrower than the rearward end thereof. This facilitates the folding operation as will hereinafter be more fully described.

A liquid-impervious foldable material 18 such as vinyl or the like, joins side panel edges 16a to bottom panel edges 17a to form an elongated nonrigid portion 18a between the side and bottom panels. Nonrigid portions 180 provide an important and useful purpose. When the boat is in water or the like, and a load, e.g., a person, is in the boat, the downward normal force of the load is counteracted by an upward buoyant force from the water or the like. Thus, an elongated bulge results extending along both edges of the bottom panel to produce directional guide means and directional stability. Liquid-impervious foldable material 18 further joins the adjacent ends of the side and bottom panels at their respective extremities to form a foldable forward end 18b and a foldable rearward end 180.

Secured to the inner sides of both side panels 16 and opposite each other, are channel means 19 extending normally to the major axis of the panels (see FIG. 4). Accommodated in channel means 19 is an expansion member 20 (see also FIGS. 5 and 6) which has tapered sides 20a and contoured portions 20b at the forward edge 20c thereof. The forward edge 20c of expansion member 20 engages the inner surface of bottom panel 17 while contoured portions 20b are so designed to accommodate the elongated bulges which axially extend on both sides of said bottom panel and provide directional stability. As hereinbefore mentioned, the dimension of expansion member 20 as measured across the tapered edges 20a thereof is slightly less than the maximum dimension between the side panels 16 when the latter are spread apart, but prior to tensional expansion thereof. Further, the dimension of expansion member 20 from its uppermost or trailing edge 20d to its forward edge 200 is greater than the distance between the uppermost or open end 19a of channels 19 and bottom panel 17 when the latter is spread to its utmost, but prior to tensional expansion thereof.

Again, it should be noted that although expansion member 20 is shown as a solid panel or board, said member may consist of a framework only, provided the peripheral configuration and dimensions of expansion member 20 are maintained.

Also, on the inner sides of both side panels 16 adjacent the uppermost or open end 19a of channels 19 and opposite each other, are axially coextending channels 21 (as best seen in FIG. 4) so as to form an upright T" configuration on the inside of both side panels with the normally extending channels 19. Channels 21 are provided with a gap or opening 21a where they overlie open end 19a of channels 19 to allow expansion member 20 to pass through and to further allow the expansion member to contact side panels 16. Channels 21 are further provided with a rearward or open end 21b.

It should be noted that without deviating from the scope of the invention herein, the top member 210 of channel 21 rearwardly of opening 21a may be eliminated leaving the bottom member 21d to act as a support member. In this case the rearward or open end 21b of channels 21 would terminate at a point forward of uppermost or open end 19a of channels 19 in order to insert expansion member 20 into the last mentioned channels 19. Thus, support member 21d which is similar to the bottom member of the portion of channel 21 forward of opening 21a and lies in the same plane, may be utilized to support locking member 23, particularly if the latter is to be utilized as a seat. In any event, it should be further noted that the top surface 212 of the bottom member 21d of channels 21 lies in a plane situated no lower than the uppermost point of opening 19a in channels 19.

Locking member 12 (see also FIGS. 7 and 8) is inserted into the rearward or open end 21a of channels 21 to the axial position desired. Locking pins (not shown) may be inserted through locking holes 21f carried by channels 21 and into either of the locking holes 23a carried by locking member 23 thereby maintaining the locking member in the longitudinal position selected. When the boat contains other occupants or load in addition to the initial occupant, the locking member 23, when used as a seat, may be adjusted and shifted in a longitudinal or axial direction to rebalance the boat for maximum efficiency and stability by redistributing the weight therein. Thus, regardless of the longitudinal position of the locking member relative to locking holes 21f, a corresponding locking hole 23a carried by the locking member is available.

As shown herein, locking member 23 is provided of sufficient width to form a seat for the initial occupant, i.e., rower or sailer. If, however, a seat is not desired, without deviating from the scope of the invention herein, a bar may be inserted within each channel 21 of sufficient width to prevent the edges 20a of expansion member 20 from passing beyond the uppermost or open end 19a of channels 19, or in the alternate, a frame element coextending with and engaging only the trailing or uppermost edge 20d of said expansion member and the grooves 21 serving the same purpose, may be utilized.

The expansion member 20 is inserted into channels 19 until its trailing or uppermost edge 20d passes beyond or clears the uppermost or open end 19a of said channels. Since, as aforesaid, expansion member 20 has a slightly greater width and depth than the width of the boat and depth thereof from the uppermost end of channels 19 to the bottom panel when the boat is unfolded to its maximum prior to its expansion, the side and bottom panels are outwardly expanded. Because the respective ends of the panels are joined to each other by the relatively nonexpandable liquid-impervious material 116 to form foldable ends lllb and llbc, said panel ends are restricted from outward expansion causing the side and bottom panels to bow outwardly having the apex of said bow adjacent the area contacted by the expansion member 26.

By thereafter inserting locking member 23 into axially extending channels 21, expansion member 26 is prevented from being displaced from channels l9 due to the presence of locking member 23 accommodated in channels 22 which provides a restricting abutment surface. As aforesaid, if desired, the locking member 23 may be locked into its lockingposition by the use of a pin or the like passing through the locking holes 21f and 23a carried by channels 21 and locking member 23, respectively.

Additional stability and rigidity is derived by inserting a rigid end panel 2d into normally extending channels 25 positioned at the inner side of the extremities of each side panel 116 opposite each other at the rear of the boat and a rigid end panel 26 into normally extending channels 27 at the inner side of the extremities of each side panel 116 opposite each other at the forward end of the boat.

To insure that end panels 24 and 26 are maintained in place, locking members 28 and 29 are inserted into axially extending channels 36 and 3l at the rear and forward ends of the boat, respectively. Locking members 28 and 29 are inserted until they engage the upper surface of lateral supports 2 1a and 26a carried on their inner surfaces by end panels 245 and 26, respectively. Thus, due to the accommodation of the locking members 23 and 29 in their respective channel means 30 and 311 and their engagement with lateral supports 24a and 26a, respectively, end panels 24 and 26 are prohibited from displacement from normally extending channels 25 and 27.

Locking members 28 and 29 are sufficiently wide to provide additional seating means. Further, if a sailing sabot is desired, a bore 290 may be situated in the forward locking member or seat 29 through which a mast 33 with a sail attached (not shown) may be inserted and seated in hallowed block 34 (see H0. 12). A rudder 35 having a tiller 36 may then be temporarily or permanently secured to end panel 24 by clamping means 37. (See FIG. 13). if a center board is desired, an elongated slot 17b passing through bottom panel 117 is encompassed by center board well 38 having upwardly extending side walls 33a and open ends 33b and 36c. (See FlGS. 114i, l5 and l6). The forward edge of locking member 23 will then engage the uppermost rearward edge of the center board well 33 while the uppermost forward edge thereof is retained by a crossmember 39 such as a rod or the like, which is secured to the inner surfaces of side panels l6 by brackets ill or the like. Thus, it can be seen that locking member 23 not only serves to lock expansion member into place, but also retains center board well 33 in place.

lt should be noted that center board well 33 is provided with flanges 33d and 3%. Flange 36d surrounds open ends 36b and is engaged by the forward edge of locking member 23, as aforesaid. in addition, flanges ila carried by center board ill. (see FlGS, lid and 117) seat upon flange 33d and supports center board ill in its appropriate position. Flange 32% seats upon sealing washer 42 which surrounds slot 171;. Thus, being tightly engaged by locking member 23 and crossmember 39, center board well tightly engages sealing washer $2 and prevents liquid leaking into the boat.

Oar locks 32 are provided to the upper edges of side panels 16 through which conventional oars or the like may be inserted to propel the boat. The boat may also be propelled by a marine outboard motor or the like by temporarily or permanently securing the same to end panel 24.

As hereinbefore described, the boat is quickly and easily assembled by unfolding the side panels l6 away from bottom panel l7 to a substantially vertical position. Expansion member 26 is then inserted into normally extending channels 119 and slid therein until forward edge Ztlc thereof engages bot tom panel 17 and its uppermost or trailing edge 26d clears the uppermost or open end 319a of channels l9, thereby outwardly bowing said side and bottom panels. Locking member 23 is thereafter inserted into rearward or open end 21a of axially extending channels 21 and slid forward into said channels until said locking member 26 and the latter abuts against said locking member 23.

End panels 2d and 26 are slid into normally extending channels 25 and 27, respectively, after which locking members 23 and 29 are inserted and slid into axially extending channels 36 and 31, respectively, until locking member 28 engages lateral support 2dr: on end panel 24 and locking member 29 engages lateral support 26a on end panel 26.

The boat is quickly disassembled and folded by removing locking member 23 and expansion member 26, removing locking members 26 and 29, followed by the removal of end panels 2d and 26. As a convenience, the removed members and end panels may be placed flat on the inside of the bottom panel after which one side panel 116 is folded over the bottom panel l7 and the removed end panels and members, i.e., expansion member locking member, etc., followed by folding the other side panel 16 over the first folded side panel.

it should be noted that although channels are shown herein, it is understood that block and groove means or the like may be utilized without deviating from the scope of the invention.

While one embodiment of the invention and the method of making the same has been described, it is understood that the particular embodiment of the invention herein disclosed is for illustrative purposes only and that various changes may be made therein without departing from the principles of the invention.

I claim:

l. A light-weight foldable boat, comprising:

a pair of elongated flexible side panels situated in spatially positioned arcuate planes converging at both their ends; an elongated flexible bottom panel positioned intermediate corresponding longitudinal edges of said side panel and in spatial relationship thereto, said bottom panel being situated in an arcuate plane curving opposite to the arcuate planes of the said side panels, the ends of said bottom panel converging toward the ends of said side panels;

a liquid-impervious foldable element connecting the longitudinal edge of said bottom panel and said corresponding longitudinal edges of said side panels in spatial rela tionship and connecting the corresponding converging ends of said side panels and bottom panel in spatial rela tionship so as to form an elongated open faced vessel;

first channel means secured to the inner sides of each side panel, extending normal to the major axis of said side panels and opposite to each other,

an expansion member accommodated in said first channel means below the uppermost end of said first channel means, said expansion member having a width and depth greater than the distance between said side panels and a depth greater than the distance between the open end of the uppermost end of the first channel means and the bot tom panel prior to the outward expansion of the side and bottom panels, so that said side and bottom panels are outwardly bowed from the cavity of said vessel, the apexes of said bows occuring in said side and bottom panels in the area of contact thereof by said expansion member;

second channel means secured to the inner side of each side panel extending axially with the major axis of said side panels and opposite to each other adjacent to the uppermost end of said first channel means,

a locking member accommodated in said second channel means so as to overlap and abut against the uppermost edge of said expansion member, thereby preventing the latter from displacement normal to the major axis of said vessel; and

means for providing rigidity to the forward and rearward ends of said vessel.

2. A semi-rigid foldable boat as described in claim 1, wherein said locking member is provided with a means for locking the same accommodated within said second channel means.

3. A semi-rigid foldable boat as described in claim 1, wherein the first and second channel means forms an upright T configuration whereby the channel of the uppermost end of said first channel means and the channel of the rearmost end of said second channel means are open.

4. A semi-rigid foldable boat as described in claim 1, wherein the means for providing rigidity to the forward and rearward ends of said vessel are rigid members having a width and depth slightly greater than the width and depth of the vessel at the respective ends of said vessel, said rigid members being accommodated in groove means situated opposite each other at the extremities of each side panel and on each inner side thereof, normal to the major axes of said vessel.

5. A semi-rigid foldable boat as described in claim 3, wherein the second channel means adjacent the open end of said first channel means is provided with a slot so as to permit v the passage therethrough of the expansion member.

6. A semi-rigid foldable boat as described in claim 5, wherein the locking means is a flat panel having the ends thereof accommodated in each second channel means and the edges thereof extending before and behind the uppermost edge of said expansion member so as to form a flat seat to accommodate an occupant of the vessel.

7. A semi-rigid foldable boat as described in claim 4, wherein the axially extending channel means are positioned opposite each other adjacent the rearward and forward end of the side panels, fiat panels being accommodated in each pair of channel means at each end of the vessel to form seats, said rigid members at the respective end of said vessel are provided with support means extending axially into a cavity of said vessel to form supports for the forward and rearward flat panels, respectively.

8. A sembrigid foldable boat as described in claim 6, wherein said seat is adjustable in a direction axial to the major axis of the vessel to provide a means for balancing the loads within said vessel relative to the center of gravity thereof.

9. A semi-rigid foldable boat as described in claim 7, wherein the bottom panel is provided with a slot therethrough extending axially with the major axis of the vessel, side walls extending upwardly therefrom into the vessel cavity, the rearward uppermost edge of said side walls engaging and abutting against the underside of the forward edge of said seat and the forward edge thereof engaging and abutting against a reten sion member extending normally to the vessel cavity and secured at its opposite extremities to the side panels, a flat elongated member loosely accommodated within said side walls and extending through said slot in the bottom panel to form a center board, means for securing a sail or the like provided at the forward end of said vessel, and means for securing a tiller or rudder provided to the rearward end of said vessel.

10. A semi-rigid foldable boat as described in claim 9, wherein the means for securing the sail is a mast extending through a bore in the flat panel situated in the axially extending channel in the forward end of said vessel and accommodated in a cavity provided in the inner side of said bottom panel, and the means for securing said tiller and rudder is a bracket carrying the tiller and rudder means secured to the rearward rigid member by bolts or the like. 

1. A light-weight foldable boat, comprising: a pair of elongated flexible side panels situated in spatially positioned arcuate planes converging at both their ends; an elongated flexible bottom panel positioned intermediate corresponding longitudinal edges of said side panel and in spatial relationship thereto, said bottom panel being situated in an arcuate plane curving opposite to the arcuate planes of the said side panels, the ends of said bottom panel converging toward the ends of said side panels; a liquid-impervious foldable element connecting the longitudinal edge of said bottom panel and said corresponding longitudinal edges of said side panels in spatial relationship and connecting the corresponding converging ends of said side panels and bottom panel in spatial relationship so as to form an elongated open faced vessel; first channel means secured to the inner sides of each side panel, extending normal to the major axis of said side panels and opposite to each other, an expansion member accommodated in said first channel means below the uppermost end of said first channel means, said expansion member having a width and depth greater than the distance between said side panels and a depth greater than the distance between the open end of the uppermost end of the first channel means and the bottom panel prior to the outward expansion of the side and bottom panels, so that said side and bottom panels are outwardly bowed from the cavity of said vessel, the apexes of said bows occuring in said side and bottom panels in the area of contact thereof by said expansion member; second channel means secured to the inner side of each side panel extending axially with the major axis of said side panels and opposite to each other adjacent to the uppermost end of said first channel means; a locking member accommodated in said second channel means so as to overlap and abut against the uppermost edge of said expansion member, thereby preventing the latter from displacement normal to the major axis of said vessel; and means for providing rigidity to the forward and rearward ends of said vessel.
 2. A semi-rigid foldable boat as described in claim 1, wherein said locking member is provided with a means for locking the same accommodated within said second channel means.
 3. A semi-rigid foldable boat as described in claim 1, wherein the first and second channel means form an upright ''''T'''' configuration whereby the channel of the uppermost end of said first channel means and the channel of the rearmost end of said second channel means are open.
 4. A semi-rigid foldable boat as described in claim 1, wherein the means for providing rigidity to the forward and rearward ends of said vessel are rigid members having a width and depth slightly greater than the width and depth of the vessel at the respective ends of said vessel, said rigid members being accommodated in groove means situated opposite each other at the extremities of each side panel and on each inner side thereof, normal to the major axes of said vessel.
 5. A semi-rigid foldable boat as described in claim 3, wherein the second channel means adjacent the open end of said first channel means is provided with a slot so as to permit the passage therethrough of the expansion member.
 6. A semi-rigid foldable boat as described in claim 5, wherein the locking member is a flat panel having the ends thereof accommodated in each second channel means and the edges thereof extending before and behind the uppermost edge of said expansion member so as to form a flat seat to accommodate an occupant of the vessel.
 7. A semi-rigid foldable boat as described in claim 4, wherein the axially extending channel means are positioned opposite each other adjacent the rearward and forward ends of the side panels, flat panels being accommodated in each pair of channel means at each end of the vessel to form seats, said rigid members at the respective end of said vessel are provided with support means extending axially into the cavity of said vessel to form supports for the forward and rearward flat panels, respectively.
 8. A semi-rigid foldable boat as described in claim 6, wherein said seat is adjustable in a direction axial to the major axis of the vessel to provide a means for balancing the loads within said vessel relative to the center of gravity thereof.
 9. A semi-rigid foldable boat as described in claim 7, wherein the bottom panel is provided with a slot therethrough extending axially with the major axis of the vessel, side walls extending upwardly therefrom into the vessel cavity, the rearward uppermost edge of said side walls engaging and abutting against the underside of the forward edge of said seat and the forward edge thereof engaging and abutting against a retension member extending normally to the vessel cavity and secured at its opposite extremities to the side panels, a flat elongated member loosely accommodated within said side walls and extending through said slot in the bottom panel to form a center board, means for securing a sail or the like provided at the forward end of said vessel, and means for securing a tiller and rudder provided to the rearward end of said vessel.
 10. A semi-rigid foldable boat as described in claim 9, wherein the means for securing the sail is a mast extending through a bore in the flat panel situated in the axially extending channel in the forward end of said vessel and accommodated in a cavity provided in the inner side of said bottom panel, and the means for securing said tiller and rudder is a bracket carrying the tiller and rudder means secured to the rearward rigid member by bolts or the like. 